1221661373635 has 4 divisors (see below), whose sum is σ = 1465993648368. Its totient is φ = 977329098904.

The previous prime is 1221661373593. The next prime is 1221661373651. The reversal of 1221661373635 is 5363731661221.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 1221661373635 - 2²³ = 1221652985027 is a prime.

It is a super-2 number, since 2×1221661373635² (a number of 25 digits) contains 22 as substring.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 122166137359 + ... + 122166137368.

It is an arithmetic number, because the mean of its divisors is an integer number (366498412092).

Almost surely, 2^{1221661373635} is an apocalyptic number.

1221661373635 is a deficient number, since it is larger than the sum of its proper divisors (244332274733).

1221661373635 is an equidigital number, since it uses as much as digits as its factorization.

1221661373635 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 244332274732.

The product of its digits is 816480, while the sum is 46.

The spelling of 1221661373635 in words is "one trillion, two hundred twenty-one billion, six hundred sixty-one million, three hundred seventy-three thousand, six hundred thirty-five".